1,721,199 research outputs found
Formulation development of poorly water-soluble compounds using solubility enhancement methods
No full textAbstract: Formulation development of two poorly water-soluble compounds, UAMC 00523 (developed by the Medicinal Chemistry Laboratory of the University of Antwerp) and mangiferin, has been performed using the following techniques: cyclodextrin complexation, PLGA nanoparticle formulations, amorphous solid dispersions and dry amorphization with mesoporous silica. UAMC 00523 is a non-nucleoside transcriptase derivate with potential activity against Human African Trypanosomiasis. Mangiferin is a natural compound with a broad range of potential health-improving activities including anti-inflammatory, anticancer and antidiabetic effects. UAMC 00523 was first formulated with different ?-cyclodextrin derivatives, with a maximum solubility enhancement factor of 80. This formulation was tested in vivo (performed by the Laboratory of Microbiology, Hygiene and Parasitology of the University of Antwerp) with no detectable effect. Subsequently, PLGA nanoparticle formulations were prepared with different PLGA\u2019s and different preparation conditions. Formulations were tested in a 50 mg/kg concentration in vivo after oral administration with no detectable effect. Next, a metabolic stability study was performed, confirming the lack of in vivo activity due to the extensive metabolic clearance of the compound. Mangiferin was formulated by spray-drying of PLGA nanoparticles with an entrapment efficiency above 70% but with a low yield (less than 40%) due to the adhesion of particles on the drying chamber and the cyclone. Considering the low solubility of mangiferin in a common solvent with PLGA and the technical limitations, no further development was performed with this technique. Amorphous solid dispersions were also prepared using different HPMC grades as carrier. Partial amorphization of the compound was achieved with increased solubility. The poor solubility of mangiferin limited the further formulation development with solvent-based techniques, therefore a solvent-free method, the dry amorphization with mesoporous silica using a planetary mono mill was further applied. Binary and ternary systems have been prepared using HPMC and Soluplus\uae as third component in the formulations. By adjusting the milling settings, amorphous samples were prepared in a significantly shorter time than already reported with other carriers. The stability of the samples was evaluated at accelerated stability conditions in open and closed containers. Increased solubility and amorphous stability of 6 months were achieved for the high energy milled sample. The addition of polymer enhanced the amorphization rate of the samples and improved the stability in open and closed conditions
Identification of novel ferroptosis and necroptosis inhibitors : optimising the therapeutic potential by improving pharmacokinetic properties
No full textAbstract: Cell death can be a consequence of different stress conditions that the cells undergo, and it is relevant to maintain cell homeostasis and the integrity of multicellular organisms. In the past 20 years many novel types of non-apoptotic regulated cell death (RCD) have been identified. Particularly, ferroptosis and necroptosis emerged as new types of non-apoptotic form of cell deaths involved in the occurrence of many diseases such as neurodegenerative diseases, ischemia-reperfusion injury, ocular surface dysfunctions and cardiac diseases. Thus, ferroptosis and necroptosis inhibitors may have therapeutic potential. The work of this project focused on the design, synthesis, and biological evaluation of novel ferroptosis and necroptosis inhibitors, aiming to tackle the phospholipid hydroperoxide accumulation with radical trapping antioxidants (RTAs) for ferroptosis and inhibiting receptor-interacting serine/threonine-protein kinase 1 (RIPK1) kinases activity for necroptosis. We started from UAMC-3203 a novel RTAs developed in our group, with high potency, stability, solubility and safety in different animal models. To further improve its pharmacokinetics properties, the drug-likeness and permeability, we modified UAMC-3203 introducing different moieties leading to different series of analogues. The majority of the compounds showed high potency in the in vitro assay with an IC50 < 100 nM and in the FENIX assay a spectrophotometric method to determine lipophilic RTAs potency confirming their anti-ferroptotic potential. In addition, we previously identified GSK2656157 (GSK\u2019157), a supposedly specific inhibitor of protein kinase R (PKR)-like ER kinase (PERK), as a much more potent type II RIPK1 inhibitor. We now performed further structural optimisation on the GSK\u2019157 scaffold in order to develop a novel class of more selective Receptor-Interacting serine/threonine-Protein Kinase 1 inhibitors. Based on a structure-activity relationship (SAR) reported in the literature, we anticipated that introducing a substituent on the para-position of the pyridinyl ring would decrease the interaction with PERK. Herein, we report a series of novel GSK\u2019157 analogues with different para-substituents with increased selectivity for RIPK1. The optimisation led to UAMC-3861 as the best compound of this series in terms of activity and selectivity for RIPK1 over PERK. The most selective compounds were screened with western blot and then tested in vitro for their ability to inhibit RIPK1-dependent apoptosis and necroptosis. The docking study confirmed out hypothesis therefore leading to a novel series of potent and selective type RIPK1 inhibitors based on the GSK\u2019157 scaffold. The most promising candidates, UAMC-3844 and UAMC-3861 can be considered to study ferroptosis and necroptosis driven diseases in vivo
Discovery of necroptosis and ferroptosis inhibitors with potential applications in pathologies associated with regulated necrosis
No full textDesign, synthesis and characterization of \u3b1-amino diaryl phosphonates as serine protease inhibitors with applications in antimicrobial drug discovery
No full textAbstract: The serine protease family is the most widely studied group of proteins in biology. These enzymes are of special interest due to their notoriously diverse and well-characterized role in physiological and pathological processes. Under normal circumstances, complex and accurate systems regulate the proteolytic activity of serine proteases. Dysregulation of their function results in pathological disorders. Diaryl esters of a-amino phosphonates are a group of irreversible inhibitors of serine proteases. Their potent inhibition of serine proteases added to their absolute lack of activity against cysteine or threonine proteases confer them advantage over alternative serine protease inhibitors lacking this selectivity such as chloromethyl ketones, ketoesters or ketoamides. These attributes open for them a broad range of applications in the Medicinal Chemistry field, from the design of small molecules for target inhibition, to the synthesis of chemical tools such as ABPs. The focus of this PhD research lies on these two options. Design, synthesis and characterization of small inhibitors was undertaken for the antimicrobial drug discovery field. Increased Gram-negative bacteria resistance to antibiotics is becoming a global problem and new classes of antibiotics with novel mechanisms of action are required. The caseinolytic protease subunit P (ClpP) is a serine protease conserved among bacteria that is considered as an interesting drug target. ClpP function is involved in protein turnover and homeostasis, stress-response and virulence among other processes. The focus of this study was to identify new inhibitors of Escherichia coli ClpP and to understand their mode of action. A focused library of serine protease inhibitors based on diaryl phosphonate warheads was tested for ClpP inhibition and a chemical exploration around the hit compounds was conducted. Altogether 14 new potent inhibitors of E. coli ClpP were identified. Compounds 4.85 and 4.92 emerged as most interesting compounds from this study due to their potency and, respectively, to its moderate but consistent antibacterial properties as well as the favorable cytotoxicity profile. Utilization of a-amino diaryl phosphonates as chemical tools for the target identification was the second goal of this PhD research, focusing on the design and synthesis of activity-based probes for serine proteases involved in the patho-physiological mechanism of visceral hypersensitivity. Establishment of an efficient synthetic route with the potential of combining a variety of reporter tags in a last step was achieved. A small library of 12 ABPs with an acceptable inhibitory activity for different subclasses of serine proteases was synthesized
Strecker-type reactions and MSAS as tools for protease inhibitor discovery
No full textAbstract: In this work, two aspects of fragment-based lead discovery were explored: (1) a screening method to find a bioisosteric replacement for the carboxylate of a caspase-1 inhibitor; and (2) a protocol for a one pot reaction for combining fragment-like molecules into small inhibitor-like molecules. MSAS was developed in our group by colleagues as an improvement to SAS. MSAS advantage is to identify false negatives that are missed during the substrate screening. This was fundamental to identify isosteres since the library used did not contain any caspase substrates. The new analogues had higher IC50 values for caspase-1 than VRT-043198. One analogue had an IC50 in the nanomolar range, which would be worth to study further to determine if the bioisostere confers the molecule other advantages. The one pot protocol for a Strecker-like reaction to produce N-acylated \u3b1-amino nitriles was based on reports from the literature where similar reactions are achieved in two-step manner. We developed and optimized to a certain extent one reaction, and then explored the possibility of producing a diverse library of peptide-like compounds. These compounds are potential mechanism-based inhibitors of proteases. Other similar reactions were explored in a more superficial way; however, it might be worth further research. In conclusion, we were able to demonstrate the versatility of the MSAS and develop a flexible one pot reaction to synthesize N-acylated \u3b1-amino nitriles
Design, synthesis and evaluation of novel activity-based probes and inhibitors for trypsin-like serine proteases : focus on Dry eye disease (DED) and Irritable bowel syndrome (IBS)
No full textAbstract: Proteases catalyze the hydrolysis of peptides or proteins by cleaving peptide bonds. These enzymes are of great interest in biomedical research due to their involvement in many physiological processes. In this thesis, we focus on serine proteases. Serine proteases are involved in several physiological processes, including immune response, cell death, and tissue healing. The upregulation of these proteases can increase inflammatory cytokines, degradation of extracellular matrix components, among others. We previously obtained an in vivo proof of concept with a multi-target serine protease inhibitor (UAMC-00050) in Dry Eye Disease (DED) and Irritable Bowel Syndrome (IBS). Topical application of this compound in the eye of a tear-deficient dry eye rat animal model reduced both tissue damage and inflammatory parameters. Moreover, UAMC-00050 also causes a decrease in visceral hypersensitivity in a rat model of post-inflammatory visceral hypersensitivity. The focus of this project was to characterize the proteases involved in DED and IBS. We wanted to use a proteomic technique, activity-based protein profiling (ABPP). ABPP uses chemical probes, known as activity-based probes (ABPs), which react covalently with the active form of the target enzyme. These allow detection, visualization, or affinity purification of the labeled enzymes. During this project, we developed an extensive library of ABPs with \u201cclickable\u201d affinity tags and a diaryl phosphonate warhead. A wide diversity was achieved by including natural amino acid analogs as well as basic polar residues as side chains. A detailed enzymatic characterization was performed in a panel of trypsin-like serine proteases. Their inhibitory potencies and kinetic profile were examined, and their IC50 values, mechanism of inhibition, and kinetic constants were determined. Surprisingly, some of the high-affinity probes presented a reversible inhibitory mechanism. For the first time, we demonstrated that not only irreversible probes but also reversible probes can tightly label recombinant proteases and proteases released from human mast cells. Even under denaturing SDS-PAGE conditions, reversible slow-tight-binding probes can label proteases due to the formation of high-affinity complexes and slow dissociation rates. In further studies, we aim to identify upregulated proteases in DED and IBS biological samples. Finally, given the promising in vitro results of the ABPs with recombinant enzymes, we developed two new inhibitors targeting trypsin-like serine proteases. The results of their inhibitory potencies for a panel of trypsin-like serine proteases and the first study of their physicochemical properties showed a promising backup compound with the potential to be a therapeutic agent for DED and IBS
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Identification, lead optimization and validation of necroptosis and ferroptosis inhibitors
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